Photoprotection due to pigmentation and epidermal thickness after repeated exposure to ultraviolet light and psoralen plus ultraviolet A therapy
| Autor: | H. C. Wulf, N. Bech-Thomsen |
|---|---|
| Rok vydání: | 1995 |
| Předmět: |
Adult
medicine.medical_specialty Ultraviolet Rays medicine.medical_treatment Immunology Skin Pigmentation Human skin Dermatology Melanin chemistry.chemical_compound medicine Ultraviolet light Humans Psoriasis Immunology and Allergy Radiology Nuclear Medicine and imaging Irradiation PUVA Therapy Psoralen Aged Skin integumentary system Epidermis (botany) business.industry General Medicine Middle Aged chemistry Erythema Photoprotection PUVA therapy sense organs business |
| Zdroj: | Photodermatology, Photoimmunology & Photomedicine. 11:213-218 |
| ISSN: | 0905-4383 |
| DOI: | 10.1111/j.1600-0781.1995.tb00172.x |
| Popis: | Tanning and thickening of the epidermis are cardinal defensive responses of human skin to ultraviolet (UV) radiation that lead to increased photoprotection. Earlier studies have shown that skin pigmentation can be used to predict minimal erythema dose and minimal phototoxic dose. In this study it was calculated how much of the increase in photoprotection after 4 weeks of repeated exposure to suberythemogenic doses of either UVA or UVB radiation sources or psoralen plus UVA (PUVA) therapy that was attributable to melanogenesis. The backs of 12 volunteers were exposed to 6 different UVA and UVB radiation sources 9 times during 4 weeks. Skin pigmentation was assessed by skin reflectance measuring. Photoprotection was determined from the minimal erythema dose. Melanogenesis accounted for 63-95% of the increase in photoprotection after 4 weeks of exposure to UVA radiation. Exposure to two UVB sources induced a significant increase in photoprotection but not in pigmentation. Melanogenesis accounted only for 6-11% of the increase in photoprotection after 4 weeks of UVB exposure. The pigmentary and photoprotective responses to PUVA therapy were followed in 14 patients. After 2 weeks of exposure, the increase in photoprotection was significantly higher than predicted from the increase in skin pigmentation. After 4 weeks, melanogenesis accounted for only 36% of the increase in photoprotection. This study shows that melanogenesis accounts for the increased photoprotection after 2 weeks of exposure to UVA radiation, but after 4 weeks other protective mechanisms occur. During suberythemal UVB exposure and during PUVA therapy the importance of skin pigmentation in the overall photoprotection gradually decreases during a 4-week irradiation period. |
| Databáze: | OpenAIRE |
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